Full Circle Full Circle -- the physics and astronomy the physics and astronomy

connectionconnection

Physics, the study of our natural world, grew out Physics, the study of our natural world, grew out of astronomy and especially the work of Kepler, of astronomy and especially the work of Kepler, Galileo and Newton which showed how we could Galileo and Newton which showed how we could describe and understand planetary motion. describe and understand planetary motion.

In the last hundred years has physics has yielded a In the last hundred years has physics has yielded a completely new and unexpectedly strange view of completely new and unexpectedly strange view of the stuff the universe is made of.the stuff the universe is made of.

Currently, Physics and Astronomy are reuniting in Currently, Physics and Astronomy are reuniting in the age old attempt to understand the origins of the age old attempt to understand the origins of our universe and its remarkable evolution.our universe and its remarkable evolution.

IllusionsIllusionsOur view of the world is shaped by experience that is limited toOur view of the world is shaped by experience that is limited toobserving ordinary sized things moving at ordinary velocities. observing ordinary sized things moving at ordinary velocities. Small Small things and things that move fast behave very differentlythings and things that move fast behave very differently

Our senses are finely tuned to give us the sharpest sight, heariOur senses are finely tuned to give us the sharpest sight, hearing, ng, touch and taste possible without revealing what the real world itouch and taste possible without revealing what the real world is like. s like. Stuff that looks solid is mostly empty space and the bits of it Stuff that looks solid is mostly empty space and the bits of it can behave like can behave like waves.waves.

We think of space as something fixed and unchangeable We think of space as something fixed and unchangeable --something something that we and all things are in. that we and all things are in. But space can be warped by massive objects.But space can be warped by massive objects.

Time seems to be something universal that is the same for everyoTime seems to be something universal that is the same for everyone. ne. But atomic clocks kept on airplanes run slower than those on theBut atomic clocks kept on airplanes run slower than those on the ground.ground.

We are stuck with a lot of illusions!We are stuck with a lot of illusions!

Seeing with instrumentsSeeing with instrumentsEver since Galileo wrote Ever since Galileo wrote ““The Starry MessengerThe Starry Messenger”” 390 390 years ago and described what he could see with a years ago and described what he could see with a telescope, science has relied on instruments. telescope, science has relied on instruments.

Today we Today we ““seesee”” a universe of 10a universe of 102626 m in size with the m in size with the aid of radio telescopes and can trace the evolution of aid of radio telescopes and can trace the evolution of the universe back to a time of one part in 10the universe back to a time of one part in 104343 of a of a second from the time of the big bang second from the time of the big bang

With the aid of accelerators we can With the aid of accelerators we can ““seesee”” the minute the minute particles called Quarks and Leptons that are the particles called Quarks and Leptons that are the modern modern ““AtomsAtoms”” of which the material universe is of which the material universe is made. made.

Unfortunately the things we Unfortunately the things we ““seesee”” with instruments donwith instruments don’’t fit the t fit the neat world view of our illusions.neat world view of our illusions.

Big and Small StuffBig and Small Stuff

The largest thing we can “see” is the Universe. It is more than 10 billion light years across*.

The smallest things we can “see”so far are elementary particles with sizes of 10-22 m**.

We humans are 1 to 2 m in size. That puts us roughly in the middle of the range of sizes .

*100,000,000,000,000,000,000,000,000 m**1/10,000,000,000,000,000,000,000 m

The Small StuffThe Small Stuff

The matter in the universe is made up of just 2 The matter in the universe is made up of just 2 kinds of bits:kinds of bits:--

Quarks Quarks LeptonsLeptons

One of our guys helped discover the One of our guys helped discover the QuarkQuark

Dick TaylorDick Taylorfrom Medicine Hat, Albertafrom Medicine Hat, Albertashared a Nobel Prize the first shared a Nobel Prize the first experiment to experiment to ““seesee”” the bits wethe bits wecall quarkscall quarks

And And -- he has an ETX scopehe has an ETX scope

How Particles How Particles InteractInteract

There are just There are just 4 forces4 forcesresponsible for the responsible for the interactions between interactions between particles.particles.

Each Force works Each Force works through an exchange of through an exchange of something something -- a a bosonboson

So how do exchange forces work?So how do exchange forces work?

Imagine two people on ice skatestossing a bean bag back and forth. The sequence might go like this -

• The first person tosses a bag and recoils backward.

• The bag travels to the second person

• The second person catches it and recoils in the direction the bag was traveling.

Now the Now the tricky (and fun) part(and fun) part

The exchange forces between elementary The exchange forces between elementary particles involve very small things moving very particles involve very small things moving very fast. fast. They have They have different rules of engagementdifferent rules of engagement ––

the Quantum nature of small stuffthe Quantum nature of small stuffandand

Relativity Relativity

Quantum UncertaintyQuantum Uncertainty

The exact locations and The exact locations and motions of small things are motions of small things are hard to pin down. hard to pin down.

Planets follow smooth and Planets follow smooth and predictable orbits but predictable orbits but electrons in an atom are all electrons in an atom are all over the place . over the place .

The paths of large things are The paths of large things are predictable but those of predictable but those of electrons and quarks are electrons and quarks are fuzzy. fuzzy.

If it weren’t for this stars would collapse under their own gravity

Time of events?Time of events?

Different observers no Different observers no longer agree on when longer agree on when something happens.something happens.

Even the time sequence Even the time sequence of events can differ.of events can differ.

E=mc2?It is a necessary consequence of a maximum velocity.

Beanbags (or Bosons)?No action at a distance -even interactions have a maximum velocity.

Perhaps the strangest result of all Perhaps the strangest result of all --Space is warpedSpace is warped

When Einstein examined the full implications of When Einstein examined the full implications of a maximum velocity, he arrived at the a maximum velocity, he arrived at the conclusion that massive objects must warp the conclusion that massive objects must warp the space around them.space around them.

This was spectacularly confirmed when light This was spectacularly confirmed when light from a star passing very close to the sun was from a star passing very close to the sun was bent exactly as Einstein predicted.bent exactly as Einstein predicted.

Back to the interactionsBack to the interactions

Rules of Engagement –

• Quantum uncertainty means we can’t be sure where the particles are exactly.

• Relativity means different observers will see the events differently.

• The maximum velocity of things means there is a maximum slope to the paths.

Quantum SpilloverQuantum Spillover

An electron passes through an electric field. It is wavelike and refracted just as a light wave would be.

In the lower diagram, the maximum slope of the path is shown and the electron can’t be deflected beyond that path – or can it?

Feynman to the rescueFeynman to the rescue

Richard Feynman’s interpretation - The electron emits a photon as it enters the field and absorbs one as it leaves.

Here an electron goes backward in time!Feynman thought this might be equivalent to a positive electron or positron going forward. In that case a photon disappears to produce an electron positron pair. This is creation of matter out of energy just as E=mc2implies.

Positrons FoundPositrons FoundIn 1932 Carl Anderson, a young professor at the California Institute of Technology, was studying showers of cosmic particles in a cloud chamber and saw a track left by "something positively charged, and with the same mass as an electron". After nearly one year of effort and observation, he decided the tracks were actually antielectrons, each produced alongside an electron from the impact of cosmic rays in the cloud chamber. He called the antielectron a "positron", for its positive charge.

The discovery gave Anderson the Nobel Prizein 1936 and proved the existence of antiparticles as predicted by Dirac.

Today we can create all kinds of particles Today we can create all kinds of particles

LEP (Large electron positron LEP (Large electron positron ColliderCollider))

27 km Tunnel27 km Tunnel

The detectorsThe detectors

Detector Detector ComponentsComponents

This is the inside structure of the OPAL detector.

It consists of layers of sub-detectors, each of which is used to observe a different property of the outgoing particles

Example eventsExample events

Surprisingly simple?Surprisingly simple?

One of the results of accelerator experiments is One of the results of accelerator experiments is that the electromagnetic and weak forces are that the electromagnetic and weak forces are connected.connected.It may be that all of the forces of nature are part It may be that all of the forces of nature are part of a single basic force.of a single basic force.

What are the implications for the early Universe? What are the implications for the early Universe?

From particles to UniverseFrom particles to Universe

1010--4343s s -- quarks and leptons. The universe doubles in size every quarks and leptons. The universe doubles in size every 1010--3434s. s. 1010--3232s s -- Inflation stops. Inflation stops. 1010--44s s -- Protons and Neutrons form from quarks.Protons and Neutrons form from quarks.3 min 3 min -- Nuclei form.Nuclei form.300,000 yr. 300,000 yr. -- Atoms form. Universe becomes transparent.Atoms form. Universe becomes transparent.1B yr 1B yr -- Galaxies formGalaxies form

13B yr 13B yr –– Humans wonder where it all came fromHumans wonder where it all came from

Current puzzlesCurrent puzzles

What is it that gives mass to What is it that gives mass to the quarks and leptons? the quarks and leptons? Search about to begin at Search about to begin at CERNCERN

What about dark matter and What about dark matter and dark energy?dark energy?Lots of experiments in Lots of experiments in preparation and under way preparation and under way ––stay tunedstay tuned

Can we make a back hole?Can we make a back hole?We are about to try at CERNWe are about to try at CERN

So what have we learned?So what have we learned?

The The ““worldworld”” ((ieie: the Universe) is : the Universe) is a very big placea very big place. It is . It is unbelievably complex when we observe all the amazing unbelievably complex when we observe all the amazing things in it but things in it but astonishingly simple on the largest scaleastonishingly simple on the largest scale..

The matter in the universe appears to be made of The matter in the universe appears to be made of just two just two kinds of stuffkinds of stuff, quarks and leptons., quarks and leptons.

The forces that holds things together are of only 4 (now 3) The forces that holds things together are of only 4 (now 3) kinds and there are hints that they may all be different kinds and there are hints that they may all be different aspects of a aspects of a single force. (?)single force. (?)

Weird results Weird results but they workbut they work

Quantum and Relativity effects have made particle physics very different from what anyone expected. But the price of being a scientist is that you have to believe in observations and the observations bear out all of this and more.

the endthe end

Physics isnPhysics isn’’t really hard but it is definitely weird. t really hard but it is definitely weird.

I guess thatI guess that’’s why I like it.s why I like it.